Reflective structured optical sheets such as that taught by U.S. Pat. No. 4,799,137 can be used to intercept and redirect incident light. In this reference the incident light is redirected through a design angle (ninety degrees) by refractive optical elements in combination with a reflective mirror coating. This is one example of a directed reflection optical device. The inclusion of a mirror in the composite structure requires vapor coating a metallic layer on the transparent plastic film or body portion of the device. Such metallic layers are optically inefficient, expensive to apply and can preferentially suffer environmental degradation.
This type of device exhibits what may be called "single axis stability". The input light beam and the output bear a fixed angular relationship even when the device is rotated slightly about one axis. This property can be exploited in some applications.